ADP-ribosyl cyclase 2 (also known as Bone marrow stromal antigen 1 (BST1) or CD157) is a lipid-anchored, bi-functional ectoenzyme that catalyses ribonucleotide cyclisation and hydrolysis. It generates the nucleotide second messengers cyclic ADP-ribose and ADP-ribose that are capable of activating calcium release and protein phosphorylation (FEBS Lett. 1994, 356(2-3):244-8). It is able to support growth of pre-B cells in a paracrine fashion, possibly through generation of NAD+ metabolites (Proc. Natl. Acad. Sci. USA 1994, 91:5325-5329; J Biol Chem. 2005, 280:5343-5349).
ADP-ribosyl cyclase 2 and its homolog, CD38, appear to act as receptors, generating second messenger metabolites that induce intracellular Ca2+ release via the ryanodine receptor (Biochem Biophys Res Commun. 1996, 228(3):838-45). It may also act via CD11integrin to effect Ca2+ release through the PI-3 Kinase pathway (J Biol Regul Homeost Agents. 2007; 21(1-2):5-11). BST1 has not been previously reported to originate from acute myeloid leukemia (AML), breast cancer, colorectal cancer, kidney cancer, lung cancer or pancreatic cancer cell membranes and represents a protein of new therapeutic and diagnostic value. BST1 is also shown to be expressed on monocytes and granulocytes, both of which can be associated with and activated in diseases such as asthma, gout, crohns, lupus and diabetes. Monocytes are also implicated in the development of atherosclerotic plaques.